Electronically controlled fluid coupling device

ABSTRACT

An electronically-controlled fluid coupling device having a front mounted fan and electrical actuation without a tethered harness. The fluid coupling device combines an inverted viscous clutch, drive pulley and a split electromagnetic actuator package. In this arrangement, the electrical portion of the split electromagnetic actuator is not physically attached to the fan drive, but is instead mounted to a stationary member. The remaining actuator components are integral to the fan drive and are composed of only mechanical parts. The inverted clutch arrangement having remote electronic control allows three output modes: engaged, partially engaged, or disengaged.

TECHNICAL FIELD

The invention relates generally to fan drive systems and morespecifically to an electronically controlled fluid coupling device.

BACKGROUND ART

The present invention relates to fluid coupling devices of the typeincluding both fluid operating chamber and a fluid reservoir chamber,and valving which controls the quantity of fluid in the operatingchamber.

Although the present invention may be used advantageously in fluidcoupling devices having various configurations and applications, it isespecially advantageous in a coupling device of the type used to drive aradiator cooling fan of an internal combustion engine, and will bedescribed in connection therewith.

Fluid coupling devices (“fan drives”) of the viscous shear type havebeen popular for many years for driving engine cooling fans, primarilybecause their use results in substantial saving of engine horsepower.The typical fluid coupling device operates in the engaged, relativelyhigher speed condition only when cooling is needed, and operates in adisengaged, relatively lower speed condition when little or no coolingis required. Today, electrically actuated viscous fan drives arecommonplace because they can be precisely controlled between an engaged,partially engaged, and disengaged mode to control output at a given fanspeed as determined by the vehicle's engine computer.

Today's electrically actuated viscous fan drives have the actuatormounted to either the front or the rear side of the fan drive. In bothcases, the actuators are mounted to the drives through a ball bearingand the stationary electrical wires are then tethered to a stationarylocation on the engine or shroud or whatever optimum for the particularcustomer application. The length of tether for front mount actuatorsbecomes a limiting factor for large fan applications and the axiallength of the rear mount actuator limits the use from narrow packageapplications. Durability of either design is a function of bearing lifeand tether life. Ideally, a fan drive without a tether would bepreferred if this improves durability and lowers cost while sustainingfan drive performance attributes.

The front mounted electrical actuator was result of an evolution ofearlier air-actuated viscous fan drives used in heavy truck and largebus applications. The bi-metal control spring on the front of theviscous drive was simply replaced by a bearing mounted pneumaticsolenoid. Durability issues with the tether and higher fuel economyrequirements forced the heavy-duty industry to switch to pneumaticon-off friction clutches with no tether (air supply coming through thecenter of the mounting bracket-pulley subassembly). Today the heavy-dutyindustry is now facing even stiffer fuel economy and noise controlrequirements which has forced a need for variable speed or at leastmulti-speed fan drives. As a result, viscous drives are being consideredagain which has lead to the need for rear-actuated viscous fan drive.Subsequently, a rear mount electrical actuator was developed which hashelped reduce potential tether durability problems associated with thefront mount style actuator and in addition provides the customer aneasier means to install the fan drive and associated tether.

Front actuated viscous fan drives continue to exist though for light tomedium duty applications because the axial length and cost are betterthan rear actuated. However, in some light duty gas engine applicationswhere the fan clutch is driven by the waterpump, a system resonanceproblem exists caused by numerous factors including mass and cg of thefan drive.

SUMMARY OF THE INVENTION

The present invention is intended to minimize the aforementionedproblems with tethered actuators and system resonance whileincorporating desirable features such as a high-speed reservoir and acombined “failsafe” and anti-drainback option.

The present invention enables a viscous fan drive with a front-mountedfan and electrical actuation without a tethered harness. The device ofthe present invention combines an inverted viscous clutch, a drivepulley and a split electromagnetic actuator resulting in a purelymechanical package that provides several advantages over existingengine-driven electronically managed viscous fan drives. An invertedclutch is one where the conventional clutch is essentially flippedaround such that the central shaft is the output shaft while the finnedmembers are the input.

In this configuration, the electrical portion of the actuator is notphysically attached to the fan drive but rather is mounted to astationary member of the drive pulley. The remaining actuator componentsare integral to the fan drive and as a result the fan drive itself haspurely mechanical parts. The arrangement allows for fast response timesto engage or disengage the clutch and also allows for open loop controlof the electrical actuation.

Other features, benefits and advantages of the present invention willbecome apparent from the following description of the invention, whenviewed in accordance with the attached drawings and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 an exploded perspective view of the major components of anelectronically controlled fluid coupling device according to onepreferred embodiment of the present invention;

FIG. 2 is section view of an assembled electronically controlled fluidcoupling device of FIG. 1; and

FIG. 3 an exploded perspective view of the electronically controlledfluid coupling device of FIG. 2.

BEST MODES(S) FOR CARRYING OUT THE INVENTION

Referring now to the drawings, which are not intended to limit theinvention, FIGS. 1–3 illustrates one preferred form of a fluid couplingdevice 10 (“viscous fan drive”) of a type utilizing the presentinvention. As best shown in FIG. 1, the fluid coupling device consistsof three major subassemblies, including a fan drive subassembly 5, anelectromagnet subassembly 7, and a waterpump subassembly 9. Thewaterpump subassembly 9, shown here as an engine-mounted waterpumpsubassembly 9 driven by a crankshaft pulley system, could also be astand-alone bracket-pulley subassembly. As shown in FIG. 2, theelectromagnet subassembly 7 is mounted to the stationary waterpumphousing and the fan drive subassembly 5 mounts to the waterpumpsubassembly 9.

As best shown in FIGS. 2 and 3, the fan drive subassembly 5 includes anoutput shaft 20, a body 22, a ball bearing 24, a rotor 26, a reservoirplate 28 having a fill port 29, a cover 30, a torsion spring 31 anarmature valve subassembly 32 having an attached valve arm 33, a gasket34, a bushing 36, a pulley 38, a pole 40, a second gasket 42, a hub 44,and a plurality of rivets 46. The body 22 and cover 30 are preferablyfinned along their respective outer peripheries.

The electromagnetic subassembly 7 includes a coil 48 and steel housing50 that is mounted to the stationary waterpump subassembly 9. The coil48 has a wire harness 52 that is electrically coupled to a controller 54and power source 55. The controller 54 receives electrical signals froma plurality of engine sensors 57 regarding engine and vehicle operatingconditions. The controller 54 interprets these signals to direct thepower source 55 to send electrical current to the coil 48 via the wireharness 52 to control the output from the fluid coupling device 10 in amanner described in more detail below. Other elements of theelectromagnetic circuit contained with the fan drive subassembly 5include the pole 40, the armature valve subassembly 32, the hub 44 andpulley 38. Further, the threaded steel adapter 62 on the waterpumpsubassembly 9 completes the electromagnetic circuit.

As shown in FIGS. 1 and 2, the waterpump subassembly 9 consists of acentral rotatable waterpump shaft 56 bearing mounted within a stationaryhousing 58 which is mounted directly to the engine block face (notshown) near the crankshaft pulley (not shown) via mounting holes 60using bolts (not shown). In an alternative preferred embodiment (notshown), the waterpump subassembly could be a stand-alone bracket-pulleysubassembly. The waterpump shaft 56 is coupled to a plurality ofimpellers (not shown) used to control engine coolant flow within anengine cooling system to cool the engine. As best shown in FIG. 2, thepulley is coupled to the threaded steel adapter 62 of the waterpumpshaft via the hub 44 and pole piece 40. Thus, the waterpump shaft 56rotates at the same rotational rate as the pulley 38 to drive theimpellers and therein provide coolant flow to the engine.

As best seen in FIG. 2, the steel engine-driven pulley 38 is sandwichedbetween the die-cast aluminum cover 30 and the non-ferrous hub 44 by wayof rivets 46 or bolts (not shown) and sealed utilizing the first gasket34 and second gasket 42. The pulley 38 is coupled to the enginecrankshaft via a belt 70 and also provides an element of theelectromagnetic control circuit. The pulley 38 thus rotates the cover 30at a rate determined by the engine operating speed translated to thepulley 38 via the crankshaft and belt 70.

The die-cast aluminum cover 30 has an overlying region 72 that isroll-formed around the outer periphery 74 of the die-cast aluminum body22. Thus, the body 22 rotates at the same rotational rate as the cover30. The output shaft 20 is rotatably mounted within the body 22 using aball bearing 24 and is affixed to the rotor 26. The volume of spacearound rotor 26 and bounded by cover 30 and body 22 define a fluidchamber 43 having a quantity of viscous fluid (not shown), while thecover 30 and reservoir plate 28 define a fluid reservoir 41. Further, afluid reservoir 41 is fluidically coupled with the fluid chamber 43through fill port 29. The valve arm 33 covers or uncovers the fill port29, depending upon the actuation of the electrical coil 48, to controlthe flow of fluid between the fluid reservoir 41 and fluid chamber 43.In addition, the fluid chamber 43 is fluidically coupled to a workingchamber 45, defined between the rotor 26, body 22, and cover 30. Theamount of viscous fluid contained in the working chamber 45, inconjunction with the rotational speed of the cover 30 coupled to thepulley 38, determines the torque transmitted to the rotor 26 thatrotates the output shaft 20. In other words, the torque response is aresult of viscous shear within the working chamber 45.

The rotor 26 also includes a scavenge chamber 27 that returns viscousfluid from the working chamber 45 to reservoir 41. Disposed adjacent theradially outer periphery of the operating chamber 45 is a pumpingelement 25, also referred to as a “wiper” element 25, operable to engagethe relatively rotating fluid in the operating chamber 45, and generatea localized region of relatively higher fluid pressure. As a result, thepumping element 47 continually pumps a small quantity of fluid from theoperating chamber 45 back into the reservoir chamber 41 through ascavenge chamber 27, in a manner well known in the art.

While not shown, the output shaft 20 may be coupled to a fan having aplurality of fan blades. Thus, the rotation of output shaft 20 mayrotate the fan to cool the radiator or other engine components.

The pole 40 has a threaded inner portion 76 that is threaded onto thethreaded steel adapter 62. The outer periphery 78 of the pole 40 islocated between an outer projection 80 of the hub 44 and the threadedinner portion 76. The pole 40 also has a base region 82 that abuts thethreaded steel adapter 62 of the waterpump shaft 56 and extendssubstantially perpendicularly with respect to the length of the threadedinner portion 76 and extends between the hub 44 and the reservoir plate28 (is shown to the left of the threaded steel adapter 62 in FIG. 2).The pole 40 also has an inward center projection 84 that extendssubstantially perpendicular from the base region 82 and opposite theouter periphery 78. The pole 40 also has a plurality of pole pieces 86separated by gaps 88 that extend around the outer periphery of the baseregion 82.

The valve arm armature subassembly 32 has a series of tooth-likeprojections 90, or leaf-like projections 90, that extend outward from acentral region 92. The central region 92 has a central hole 94containing the non-ferrous bushing 36 that is used to pilot the valvearm armature subassembly 32 around the inward center projection 84 ofthe pole 40. When assembled, the leaf-like projections 90 slightlyoverlap the respective pole pieces 40. A torsion spring 31 coupled tothe assembly 32 maintains the projections 90 in a preset positionwherein the leaf-like projections 90 are misaligned with the respectivepole pieces 40. Upon magnetization, the projections 90 will attempt toline up with the pole pieces 40, therein rotating the subassembly 32relative to the pole pieces 40.

The valve arm 33 is coupled to the central region 92 of the valve armassembly 32 and extends towards the reservoir plate 28. The valve arm 33is cantilevered at its free end. The valve arm 33 thus rotates with thesubassembly 32 to cover or uncover the fill port 29. In an unmagnetizedstate (wherein no electrical current is flowing through the coil 48),the torsion spring 31 maintains the subassembly 32 such that the valvearm 33 is positioned wherein the fill port 29 is uncovered. Thisposition is known as the “failsafe on” position, in that fluid flowsfrom the fluid reservoir 41 to the fluid chamber 43 through the fillport 29 is maintained in the absence of electrical current flowing tothe coil 48, which maintains the rotor and output member in an engagedposition to provide cooling airflow even in the absence of electricalactuation to prevent overheating of the attached engine.

The amount of electrical power supplied in terms of pulse widthmodulation from the external controller 54 and power source 55, andhence the amount of magnetic flux available to control the relativepositioning of the valve arm 33, is determined by the externalcontroller 54. The controller 54 receives a set of electrical inputsfrom various engine sensors 57 that monitor various engine operatingconditions relating to engine temperature, fuel economy, emissions orother engine operating conditions affecting the performance of theengine. For example, one of the sensors 57 could be an engine mountedcoolant sensor or a pressure sensor mounted to the air conditioner. Thecontroller 54 has a stored look up table that determines a desiredengine operating range for a given engine speed. When the controller 54determines that one or more of these sensors 57 are sensing coolingconditions outside the desired operating range, the external controller54 will direct the power source 55 to send electrical power to the coil48 as a function of this electrical signal. Thus, for example, if theexternal controller 54 determines that the engine coolant temperature istoo low, or that the engine temperature is too low, a signal may be sentfrom the controller 54 to the power source 55 to activate the coil 48 toa desired pulse width, therein providing a magnetic field within thefluid coupling device 10. Upon magnetization, the projections 90 willattempt to line up with the pole piece 40, therein rotating thesubassembly 32 relative to the pole piece 40. The rotation of thesubassembly 32 therein causes the coupled valve arm 33 to rotate andcover the fill hole 29, therein preventing viscous fluid flow to theworking chamber 45. The reduction of viscous fluid within the workingchamber 45 minimizes shearing of the viscous fluid within the workingchamber 45 to drive the rotor 26 and output member 20. Hence, a fancoupled to the output member 20 would rotate slower in this condition tobring cooling conditions within a desired range.

Similarly, if the external controller 54 determines from one or more ofthe sensors 57 that the engine, or engine coolant temperature, is abovean undesired high range, no signal is sent from the external controller54 to the power source 55 and coil 48. The valve arm 33 is thusmaintained in a position wherein the fill port 29 is uncovered, thereinallowing maximum fluid flow from the fluid reservoir 41 to the fluidchamber 43 and to the working chamber 45. This provides maximum torqueresponse of the rotor 26 to rotate the output shaft 20. This in turnrotates the fan and fan blades to provide maximum cooling to theradiator to cool the engine coolant.

The present invention provides numerous advantages over currentlyavailable front and rear actuated viscous fan drives. For example, theelectrical portion of the actuator is not physically attached to the fandrive, but rather is mounted to a stationary member of the drive pulley.As such, there is no tethered wire harness and no actuator bearing. Thisleads to easier and less costly manufacturing, as there are no wires orconnectors. Further, the coil is easily replaced, which lowers serviceand warranty costs.

Further, the remaining actuator components are integral with the engineside of the fan drive. This leads to lower overhanging mass on the drivecomponents, which leads to higher system resonant frequency and possibleimprovements in waterpump durability. This also leads to compactpackaging, which can improve vehicle costs.

While the invention has been described in connection with oneembodiment, it will be understood that the invention is not limited tothat embodiment. On the contrary, the invention covers all alternatives,modifications, and equivalents as may be included within the spirit andscope of the appended claims.

For example, an accumulator plate could also be used in conjunction withthe reservoir plate to enable a failsafe valve arm feature yet allow ananti-drainback feature. An example of the use of an accumulator plate inconjunction with a fluid reservoir is described in U.S. application Ser.No. 10/287,325 to May et al., entitled “Electronically ControlledViscous Fan Drive”, which is herein incorporated by reference.

Further, in another alternative embodiment, the valve arm 33 could becoupled to the valve arm subassembly 32 such that it covers the fillport 29 in the absence of electrical activation of the coil 48. Thus,the clutching mechanism is engaged when current is applied from powersource 55 (“non-failsafe mode”).

Finally, in another preferred embodiment, the amount of pulse widthmodulation to said electrical coil could be such to generate a magneticfield in which the valve arm partially covers the fill port 29. Themagnetic field generated would be less than the magnetic field necessaryto rotate the subassembly 32 completely to the second position coveringthe fill port 29. This third position would allow partial engagement ofsaid rotor 26 and output at an infinite number of midlevel outputs tomore precisely control the amount of cooling available to the radiator.

1. An electronically controlled fluid coupling device comprising: anoutput member including a center shaft; an input member bearing mountedaround said output member, said input member comprising a body and acover; a stationary waterpump housing assembly bearing mounted to saidinput member; a rotor mounted to said output member and contained withinsaid cover and said body, said body and said rotor defining a workingchamber; a reservoir plate mounted to said input member, said reservoirplate having a fill port: a fluid reservoir defined between saidreservoir plate and said cover, said fluid reservoir having a quantityof viscous fluid; a fluid chamber defined between said reservoir plateand said rotor, said fluid chamber fluidically coupled to said workingchamber and fluidically coupled to said fluid reservoir through saidfill port; a rotatable armature subassembly coupled to said inputmember, said rotatable armature subassembly rotatable to any of aninfinite number of positions between a first position, a midlevelposition, and a second position; a valve arm fixedly coupled to saidrotatable armature subassembly, said valve arm capable of covering saidfill port when said rotatable armature subassembly is in said secondposition, therein preventing flow of said quantity of viscous fluid fromsaid fluid reservoir to said fluid chamber, said valve arm capable ofpartially covering said fill port when said rotatable armature is insaid midlevel position, therein allowing partial flow of said quantityof viscous fluid from said fluid reservoir to said working chamber topartially engage said rotor and said output member; an electromagneticsubassembly mounted to said stationary waterpump housing; a power sourceelectrically coupled to said electromagnetic subassembly; a controllerelectrically coupled to said power source, said controller directingsaid power source to provide an electrical current to saidelectromagnetic subassembly, wherein said electromagnetic subassemblyinduces a magnetic field in response to said electrical current, whereinsaid armature valve subassembly rotates from said first position to saidmidlevel position to said second position depending upon a strength ofsaid magnetic field.
 2. The fluid coupling device of claim 1 furthercomprising a torsion spring, said torsion spring maintaining saidrotatable armature subassembly in said first position in the absence ofsaid magnetic field.
 3. The fluid coupling device of claim 1 furthercomprising a pole coupled to input member, said pole having a pluralityof pole pieces extending outwardly from a base region.
 4. The fluidcoupling device of claim 3, wherein said rotatable armature subassemblycomprises a plurality of tooth-like projections extending form a centralregion, wherein one of said plurality of tooth-like projections alignswith a corresponding one of said plurality of pole pieces in response tosaid magnetic field.
 5. The fluid coupling device of claim 1, whereinsaid input member further comprises a belt driven pulley coupled to anon-ferrous hub.
 6. The fluid coupling device of claim 1, wherein saidinput member further comprises a waterpump shaft, said waterpump shaftcoupled to said center shaft and bearing mounted within said stationarywaterpump shaft housing.
 7. The fluid coupling device of claim 1 furthercomprising at least one sensor electrically coupled to said controller,said at least one sensor sending an electrical signal to said controlleras a function of a desired engine operating condition.
 8. Anelectronically controlled fluid coupling device comprising: an outputmember including a center shaft; an input member bearing mounted aroundsaid output member, said input member comprising a body and a cover; astationary waterpump housing assembly bearing mounted to said inputmember; a rotor mounted to said output member and contained within saidcover and said body, said body and said rotor defining a workingchamber; a reservoir plate mounted around said output member and coupledbetween said cover and said rotor, said reservoir plate having a fillport; a fluid reservoir defined between said reservoir plate and saidcover, said fluid reservoir having a quantity of viscous fluid; a fluidchamber defined between said reservoir plate and said rotor, said fluidchamber fluidically coupled to said working chamber and fluidicallycoupled to said fluid reservoir through said fill port; a rotatablearmature subassembly coupled to said input member, said rotatablearmature subassembly rotatable to any of an infinite number of positionsbetween a first position, a midlevel position, and a second position; avalve arm fixedly coupled to said rotatable armature subassembly, saidvalve arm capable of uncovering said fill port when said rotatablearmature subassembly is in said second position, therein allowing flowof said quantity of viscous fluid from said fluid reservoir to saidfluid chamber, said valve arm capable of partially covering said fillport when said rotatable armature is in said midlevel position, thereinallowing partial flow of said quantity of viscous fluid from said fluidreservoir to said working chamber to partially engage said rotor andsaid output member; an electromagnetic subassembly mounted to saidstationary waterpump housing; a power source electrically coupled tosaid electromagnetic subassembly; a controller electrically coupled tosaid power source, said controller directing said power source toprovide electrical current to said electromagnetic subassembly, whereinsaid electromagnetic subassembly induces a magnetic field in response tosaid electrical current, wherein said armature valve subassembly rotatesfrom said first position to said midlevel position to said secondposition in response depending upon a strength of said magnetic field.9. The fluid coupling device of claim 8 further comprising a torsionspring, said torsion spring maintaining said rotatable armaturesubassembly in said first position in the absence of said magneticfield.
 10. The fluid coupling device of claim 8 further comprising apole coupled to input member, said pole having a plurality of polepieces extending outwardly from a base region.
 11. The fluid couplingdevice of claim 10, wherein said rotatable armature subassemblycomprises a plurality of tooth-like projections extending form a centralregion, wherein one of said plurality of tooth-like projections alignswith a corresponding one of said plurality of pole pieces in response tosaid magnetic field.
 12. The fluid coupling device of claim 8, whereinsaid input member further comprises a belt driven pulley coupled to anon-ferrous hub.
 13. The fluid coupling device of claim 8 furthercomprising at least one sensor electrically coupled to said controller,said at least one sensor sending an electrical signal to said controlleras a function of a desired engine operating condition.
 14. A method forcontrolling the engagement of an electronically controlled fluidcoupling device, the method comprising: (a) forming the electronicallycontrolled fluid coupling device comprising: an output member includinga center shaft; an input member bearing mounted around said outputmember said input member comprising a body and a cover; a stationarywaterpump housing assembly bearing mounted to said input member; a rotormounted to said output member and contained within said cover and saidbody, said body and said rotor defining a working chamber; a reservoirplate mounted around said output member and coupled between said coverand said rotor, said reservoir plate having a fill port; a fluidreservoir defined between said reservoir plate and said cover, saidfluid reservoir having a quantity of viscous fluid; a fluid chamberdefined between said reservoir plate and said rotor, said fluid chamberfluidically coupled to said working chamber and fluidically coupled tosaid fluid reservoir through said fill port; a rotatable armaturesubassembly coupled to said input member, said rotatable armaturesubassembly rotatable between a first position and a second position; avalve arm fixedly coupled to said rotatable armature subassembly, saidvalve arm uncovering said fill port when said rotatable armaturesubassembly is in said first position and covering said fill port whensaid rotatable armature subassembly is in said second position andpartially covering said fill port in a midlevel position; anelectromagnetic subassembly mounted to said stationary waterpumphousing, said electromagnetic subassembly including a coil; a powersource electrically coupled to said coil; a controller electricallycoupled to said power source; and at least one sensor electricallycoupled to said controller; (b) measuring an engine operating conditionusing said at least one sensor at a given engine speed, said givenengine speed corresponding to a rotational speed of said input member;(c) comparing said measured engine operating condition with a desiredengine operating condition range at said given engine speed; (d)generating an electrical current within said power source when saidmeasured engine operating condition is not within said desired engineoperating condition range, wherein the generation of said electricalcurrent activates said coil, therein generating a magnetic field,wherein said magnetic field causes said rotatable armature subassemblyto rotate in response to the strength of said magnetic field from saidfirst position to either said midlevel position or said second positionto control the flow of viscous fluid from said fluid reservoir to saidworking chamber through said fill port to control the rotational rate ofsaid output member.
 15. The method of claim 14, wherein (c) comparingsaid measured engine operating condition with a desired engine operatingcondition range at said given engine speed comprises: determining adesired engine operating condition range at said given engine speed froma look-up table or an algorithm contained within said controller;comparing said measured engine operating condition to said desiredengine operating condition range; and sending a electrical signal fromsaid controller to said power source when said measured engine operatingcondition is not within said desired engine operating condition range.16. The method of claim 15, wherein (d) generating an electrical currentcomprises generating a pulse width modulation signal within said coil asa function of said electrical signal received from said controller,wherein said pulse width modulation signal creates a magnetic field,wherein said armature valve subassembly rotates in response to magneticfield from said first position to said second position, wherein saidfirst position is defined wherein said valve arm uncovers said fill portand said second position is defined wherein said valve arm covers saidfill port.
 17. The method of claim 15, wherein (d) generating anelectrical current comprises generating a pulse width modulation signalwithin said coil as a function of said electrical signal received fromsaid controller, wherein said pulse width modulation signal creates amagnetic field, wherein said armature valve subassembly rotates inresponse to magnetic field from said second position to said firstposition, wherein said first position is defined wherein said valve armuncovers said fill port and said second position is defined wherein saidvalve arm covers said fill port.
 18. The method of claim 15, wherein (d)generating an electrical current comprises generating a pulse widthmodulation signal within said coil as a function of said electricalsignal received from said controller, wherein said pulse widthmodulation signal creates a magnetic field, wherein said armature valvesubassembly rotates in response to magnetic field from said firstposition to said midlevel position, wherein said first position isdefined wherein said valve arm uncovers said fill port and said midlevelposition is defined wherein said valve arm partially covers said fillport.
 19. The method of claim 15, wherein (d) generating an electricalcurrent comprises generating a pulse width modulation signal within saidcoil as a function of said electrical signal received from saidcontroller, wherein said pulse width modulation signal creates amagnetic field, wherein said armature valve subassembly rotates inresponse to magnetic field from said second position to said midlevelposition, wherein said first position is defined wherein said valve armuncovers said fill port and said midlevel position is defined whereinsaid valve arm partially covers said fill port.